Purpose: The following lab was conducted in order to determine the iron (〖Fe〗^(2+)) content in an unknown sample by way of reduction-oxidation titration using a standardized potassium permanganate solution. Theory: Titration is one of the most commonly used methods for determining the amount or concentration of an unknown substance. Chemical analysis can be performed on redox titrations, if the following conditions are met: “The reaction is thermodynamically spontaneous enough to be stoichiometric”, “The reaction is kinetically fast enough to give operationally ‘instant’ results”, “No side reactions occur”, and “a satisfactory indicator exists”. These conditions are what makes potassium permanganate (〖KMnO〗_4) a very useful analytical oxidation agent as it easily fits the criteria. The half reactions for this system are: Oxidation of 〖Fe〗^(2+): 〖Fe〗^(2+)→ 〖Fe〗^(3+)+1e^- Reduction of 〖MnO〗_4^-: 〖MnO〗_4^-+8H_3 O^++5e^-→ 〖Mn〗^(2+)+12H_2 O Which produces the following overall equation: 〖MnO〗_4^-+8H_3 O^++5〖Fe〗^(2+)→5〖Fe〗^(3+)+〖Mn〗^(2+)+12H_2 O Equilibrium is initially obtained at a very slow rate, therefore the titration is carried out in the presence of excess sulphuric acid (H_2 〖SO〗_4) at a high temperature; in order to drastically increase the rate at which equilibrium is attained.
B) Greenhouse gases prevent heat from leaving the earth. C) If the level of greenhouse gases increases, the temperature will decrease. D) Some greenhouses gases are needed to keep the proper temperature balance. E) none of the above 3) Which of the following is TRUE? A) Stoichiometry allows prediction of the amounts of products that form in a chemical reaction based on the amounts of reactants.
Heats of Solution and Reaction Name: Cindy Hernandez Purpose: The purpose of this experiment is to decided if the chemical reactions are exothermic and endothermic. By finding the differences between each temperature. Overview: For this lab, we had three different chemicals involved NH4Cl, H2SO4, and NaOH. What we did with these chemicals was that we added water, except NaOH we added HCl, was that we combined both mixtures to determine if there was a temperature change. The reason why we're determining if their was a chemical reaction is to identify if it is exothermic or endothermic.
This was done by taking small amounts of the unknown acid. It was then placed into capillary tubes and inserted into the Bibby Sterilin Device. Starting with a high plateau to find a quick melting point and then proceeding to find an actual melting point. The next experiment that aided in finding more characterizations of unknown #2651145-PLF13 was equivalent weight. In order to find the equivalent weight a titration of the unknown acid had to be conducted.
In our lab we use a more sophisticated one which included a lid on the cup with an inserted thermometer and a stirrer. Thermochemistry is the study of the heat released or absorbed as a result of chemical reactions. The measurement of the total energy of a thermodynamic reaction is called enthalpy (q). This is the basis for Hess’s law which states that if two reactions are combined to yield a third reaction, the sum of the first two is equal to the third. The energy change is the same whether the process occurs in one step or many.
The change in enthalpy relies on the concentration of the salt solution, because different concentrations will produce different enthalpies. There is an equation to determine how much of this heat energy is lost or gained when a reaction is performed. Q = c m (T1-T2) Where: q is the energy in Joules C is the heat capacity, measured in joules per gram per degree Celsius M is the mass of the solution, measured in grams J is the joules G is the grams of water T is the temperature ΔH=ΔE + PΔV = (q p +w) – w = q p Procedure: 1. Follow instructions 1-9 in Appendix A-1 to initialize the MeasureNet workstation. a.
If the reaction is first order, its graphical representation is seen as ln[A] (natural log of concentration) vs. time, and the slope of its like is also the negative rate constant. Finally, for a second order reaction the graph is shown as 1/[A] (inverse of concentration) vs. time, and the slope of its given line is the positive rate constant. By understanding the rate law and finding the value of the correct rate constant with respect to the order of the reaction, one can determine the half-life of the crystal violet. This is because the crystal violet undergoes a decay reaction with the sodium hydroxide. According to Beer's Law, the absorbance of crystal violet is proportional to its concentration.
Knowing the different boiling points of the two liquids was useful in this experiment so that the sand bath could be heated to different temperatures to evaporate the two solvents. Once the liquid was evaporated the vapor was collected and condensed in the condenser allowing the collection of said liquid. When simple distillation occurred the liquid only evaporated and condensed one time as opposed to the fractional distillation. Fractional distillation was more accurate due to the fractionated column allowing multiple vaporization and condensation reactions to take place. Raoult’s Law was used in this experiment because it describes the vapor pressure that takes place in the experiment.
Introduction: In this experiment, calcium chloride was reacted with sodium hydroxide according to the following balanced equation: CaCl2(aq) + 2NaOH(aq) Ca(OH)2(s) +2NaCl(aq) The purpose doing this reaction was to perform stoichiometry calculations. Stoichiometry is the process of keeping track of the quantitative relationship between reactants and products in a reaction. In a stoichiometry problem, the coefficients in the balanced equation provide the correction number of moles of each substances that is needed to complete the reaction. Often in a reaction, there is a limiting reagent since the exact proportions of moles of the reactants are not present. Thus, a limiting reagent is the reactant that determines how far the reaction will go before causing the it to stop since there are fewer moles of it than the proportion requires.
* In heterogeneous equilibria two or more phases are present. * Because the concentrations of pure solids and liquids are constant, these substances are left out of the equilibrium constant expression for a heterogeneous equilibrium. Section 4 * If the concentration of all species in an equilibrium are known, the equilibrium-constant expression can be used to calculate the value of the equilibrium constant. * The changes in the concentrations of reactants and products on the way to achieving equilibrium are governed by the stoichiometry of the reaction. Section 5 * The reaction quotient, Q, is found by substituting reactant and product partial pressures or concentrations into the equilibrium constant